A solution is 40.0% by volume benzene (C6H6) in carbon tetrachloride at 20C. The vapor pressure of pure benzene at this temperature is 74.61 mmHg and its density is 0.87865 g/cm3; the vapor pressure of pure carbon tetrachloride is 91.32 mmHg and its density is 1.5940 g/cm3. If this solution is ideal, its total vapor pressure at 20C is

Question

Jeffrey Deleon

Chemistry

10 May, 01:00

A solution is 40.0% by volume benzene (C6H6) in carbon tetrachloride at 20C. The vapor pressure of pure benzene at this temperature is 74.61 mmHg and its density is 0.87865 g/cm3; the vapor pressure of pure carbon tetrachloride is 91.32 mmHg and its density is 1.5940 g/cm3. If this solution is ideal, its total vapor pressure at 20C is

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Answers (1)

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Hanna Bender · Answer 1

84.30 mm Hg

Explanation:

In 100 cm³ of solution we have: 40 cm³ C6H6 and 60 cm³ CCl4. Given the densities we can calculate their masses and number of moles, and since by Raoult's law

Ptotal = XAPºA + XBPºB

where XA = mol fraction = na / (na + nb) and PºA vapor pressure pure of pure component A

m C6H6 = 40 cm³ x 0.87865 g/cm³ = 35.146 g

mol C6H6 = 35.146 g / 78.11 g/mol = 0.45 mol

mass CCl4 = 60 cm³ x 1.5940 g/cm³ = 95.640 g

mol CCl4 = 95.640 g / 153.82 g/mol = 0.62 mol

mol tot = 1.07

XC6H6 = 0.45 / 1.07 = 0.42 XCCl4 = 0.62/1.07 = 0.58

Ptot (mmHg) = 0.42 x 74.61 +.58 x 91.32 = 84.30 mmHg